Digital Subscriber Line (xDSL, such as Asymmetric DSL, Very high data rate DSL, etc.) is used in point-to-point transmission technology, using copper twisted-pairs as transmission media. The DSL technology supports both symmetric and asymmetric transmission modes in subscriber loops of traditional POTS (a plain old telephone service), so that a transmission bottleneck of the “last kilometer” often happening between a network service provider and an end subscriber is solved. Because the xDSL provides high-bandwidth services by employing copper twisted-pairs, the investments of operators are effectively guaranteed to be returned, and the subscribers are provided with wideband services. Accordingly, the xDSL is well developed all over the world.
Asymmetric Digital Subscriber Line (ADSL) is a type of the xDSL, which is appropriate for transmitting asymmetric data streams used in personal wideband access services, wherein the amount of data of downlink streams (from a Customer Premise Equipment, CPE, to a Central Office, CO) of a personal wideband access services is extremely larger than that of uplink (from the CO to the CPE) streams. The ADSL has overpowering advantages in personal wideband access applications. Till now, more than 50,000,000 subscribers enjoy multimedia services provided by the ADSL, such as high-speed net-surfing, video services. ADSL service providers develop a new “gold mine” on the twisted-pair, making the ADSL services become another important income source besides the POTS.
According to the growing bandwidth demands of the subscribers, an access technology providing higher bandwidth and more flexible allocation of uplink and downlink bandwidths, such as the Very high data rate DSL (VDSL), is applied. Another widely used DSL technology is Single Line High Data Rate Digital Subscriber Line (G.SHDSL). The G.SHDSL is more often used by business consumers because it can provide asymmetric services.
All of the ADSL, ADSL2+ (second generation ADSL), and the VDSL employ frequencies higher than that used in traditional telephone signals (below 3.4 KHz). The frequency range of the ADSL is 25,875 KHz˜1104 KHz, the frequency range of the ADSL2+ is 25.875 KHz˜2208 KHz, and the frequency range of the VDSL may be 25 KHz˜30 MHz. As transmitting on different frequency bands, the xDSL and the POTS services can transmit in one telephone line. The mixed signals of the xDSL and the POTS services can be separated by filters set in transceivers on both ends of the telephone line. A system model of an ADSL can be referred to as a Splitter. In the system, a DSL Access Multiplexer (DSLAM) is included. The DSLAM can provide multi-path ADSL services or VDSL services.
According to the rapidly growing applications of xDSL, the amount of xDSL lines is closer to the amount of POTS lines, and may be nearly the same as that of the POTS lines eventually. The complexity, difficulty and maintenance cost of networking of the xDSL will be greatly increased if the networking mode is the same to that shown in FIG. 1. Thus, a new networking mode, that is an Integrated Voice Data (IVD) networking mode, has been employed by operators.
The IVD networking mode is shown in FIG. 2. The IVD networking system mainly includes an IVD line card set in a Multiple Services Access Node (MSAN). The IVD line card includes an xTU-C (xDSL CO unit), a POTS (traditional telephone service) process unit, and a Low Pass Filter (LPF). The IVD line card supports POTS transmission process of xDSL service. There are a series of advantages of the IVD networking mode, such as low stock cost, low networking complexity, low maintenance cost, and so on. Accordingly, the IVD networking mode may become a primary mode in the next generation network. However, a series of difficulties and problems will be brought by the use of the IVD networking. For example, the power consumption of device is relatively high. At the early stage, when the utilization ratio of xDSL line is rather low, the problem of high power consumption is much more noticeable.
As shown in FIG. 1, the DSLAM employs a centralized multiplexing mode. In this mode, the density of the utility of the DSLAM device can be increased gradually according to the increase of number of subscribers. The average utilization ratio of the DSLAM device is relatively high, and the power consumption is relatively low. A schematic diagram illustrating a relationship between the networking scale and the port utilization ratio in the DSLAM networking mode is as shown in FIG. 3.
As shown in FIG. 2, in an IVD networking mode of Multiply Service Access Node (MSAN), all wideband ports should be deployed along with narrowband ports at one time. At the early stage of networking, the ratio of wideband subscribers to narrowband subscribers is relatively low, and the power consumption of wideband part is relatively high. FIG. 4 shows the networking scale and the port utilization ratio of the IVD networking mode. The static power consumption is rather high at the early stage of networking using the IVD mode. For example, in a typical 32ch IVD, the static power consumption of 32ch POTS is around 3 W, while the static power consumption of 32ch ADSL is near 10 W when the ADSL is inactive. In an extreme case, the IVD is only used as a POTS, the power consumption of the IVD is 4 times of that of a PSTN device. The higher power consumption is obviously contrary to the operator's objective of saving network's power.
Implementations for reducing power consumption are provided currently. A method for saving power of xDSL lines in existing art includes the application of L2/L3 low power consumption mode, Power management (port power management), Power cutback, and so on.
The inventor found in the inventing process that the methods for saving power for xDSL lines in the existing art just concentrate on how to save power when the xDSL lines are active, and no feasible solution is given for saving the static power consumption when the xDSL lines are inactive.